It is not the formating that you will have issues with, it is updating your iPod via any other computer with iTunes.
Apple likes to marry your iPod to one computer, call it a control device call it easy integration, whatever you may call it, it is pain for you to do something like this.
You can't use iTunes to update your iPod via a different computer other than your home computer.
There are plenty of software solutions out there that will allow you to update your iPod without you "home" computer/iTunes, check out iLounge's software section. Rather than go in to that you might just ask your friend to just put the music that that he has directly on to the drive. The music won't show up on the iPod, but whoever owns the iPod can add the music from the drive to there iTunes and then add it to the iPod.